The Clean Air Act has been an essential tool for reducing air pollution in the United States. But standard estimation methods may overstate its impact, according to a paper in the American Economic Journal: Economic Policy.

Authors Lutz Sager and Gregor Singer reexamined the 2005 regulations targeting fine particulate matter (PM2.5) and found that improvements in air quality were closer to a 3 percent reduction in pollutants rather than the 10 percent suggested by conventional methods. However, they also found that the benefits from cleaner air may be larger than previous estimates suggested.

Sager and Singer recently spoke with Tyler Smith about methods for properly estimating regulatory impacts that feature time trends and the implications for other measures based on estimates of air quality improvements.